A photosensitive composition comprising an o-naphthoquinone diazide compound and a phenolic novolak resin has been industrially used as an exceedingly good photosensitive composition in the manufacture of lithographic plates and as a photoresist.
However, due to the properties of the phenolic novolak resin used as a major component, the composition has had drawbacks, for example, that it shows poor adherence to substrates and gives a coating film which is brittle, has poor wear resistance, and shows insufficient impression capacity when used in a lithographic plate. The applications of the composition has therefore been limited.
In order to overcome these problems, various polymers have been investigated as binders. For example, the poly(hydroxystyrene) or hydroxystyrene copolymer described in JP-B-52-41050 has undoubtedly improved film properties but has had a drawback of poor wear resistance. (The term "JP-B" as used herein means an "examined Japanese patent publication.")
On the other hand, in JP-A-63-226641 is described a positive-working photosensitive composition comprising as a binder an alkali-soluble polymer having an active imino group. (The term "JP-A" as used herein means an "unexamined published Japanese patent application.") There is a description therein to the effect that the composition is improved in film properties, adherence to substrates, and wear resistance. However, since the composition should be used in combination with a conventionally employed novolak resin so as to keep the range of proper development conditions wide, a lithographic plate having impression capacity on a sufficiently high level has not always been obtained.
Further, photosensitive compositions comprising a conventional phenolic resin have been disadvantageous in that they should be developed usually with an aqueous alkali solution having a pH as high as 13 or above and use of such a high-pH developing solution is never preferable from the standpoints of safety in handling and of treatment of the waste liquor resulting from development.